I heard a sermon by a TV evangelist yesterday (a fellow by the name of Hagee). I normally don't watch this stuff, but it was specifically pointed out to me.
He was talking about marraige, and he made a point that has stuck with me. He said that if a person is not willing to tollerate any disagreement with their ideas, then that person is likely motivated by insecurity and fear. People who are confident and unafraid have no problem hearing dissenting views. So, if you can't tollerate disagreement, look inside yourself. The problem is not with the dissenter, it's with you.
Now, I'm not a big evangelism fan, but that point fits JW's perfectly. No sort of dissention or discussion is allowed. In fact, even open exploration of ideas is prohibited. The reason - their beliefs are so shakey that they are afraid to explore them. They are fearful and insecure.